FIG 8.

PGE₂ blocks the antiviral effect of nitric oxide on PSaV infection. (A) Supernatants from mock- or PSaV-infected samples were collected, and the nitrite concentration was determined using the Griess reagent system, as described in Materials and Methods. LLC-PK cells were infected with PSaV (MOI = 1 FFU/cell) and subsequently treated with the COX-2 inhibitor NS-398 or the nitric oxide synthase inhibitor L-NAME, either singly or in combination. (B) The effect of inhibitor treatment on nitric oxide production was then determined as described for panel A. (C to E) The levels of viral titer (C), RNA (D), and protein (E) were determined by TCID₅₀, real-time reverse transcription (RT)-PCR, and Western blot analyses, respectively. GAPDH served as the loading control. The data are means and standard errors of the mean from the results of three different independent experiments. Differences were evaluated by one-way ANOVA. **, P < 0.001; ***, P < 0.0001.